References
Petr, Korbel & Milan, Novak. 2001. Encyclopedia of Minerals. Lisse, the Netherlands: Hackberry Press.
Chris, Pellant. 1990. Rocks, Minerals & Fossils of the World.: Little, Brown and Company.
Pough, Frederick. 1996. Rocks, Peterson Field Guides Rocks and Minerals. fifth edition: Houghton Mifflin Company, Boston New York.
Dixon, Dougal. 1992. The Practcial Geologist. New York, New York: Simon and Schuster / Frieside.
